Michael Keaton received solid advice from Jack Nicholson while the two were in the midst of filming the first Batman movie. Unbeknownst to the actors, the film would go on to become a box office sensation and cement the Dark Knight as a box office staple for decades to come. One could even go so far as to argue that there wouldn’t be a Marvel Cinematic Universe if Tim Burton‘s weirdly gothic film hadn’t been a smash hit. It was that huge.